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Verslues PE. Please, carefully, pass the P5C. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:663-666. [PMID: 38307518 PMCID: PMC10837010 DOI: 10.1093/jxb/erad446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2024]
Abstract
This article comments on:
Zheng Y, Cabassa-Hourton C, Eubel H, Chevreux G, Lignieres L, Crilat E, Braun H-P, Lebreton S, Savouré A. 2024. Pyrroline-5-carboxylate metabolism protein complex detected in Arabidopsis thaliana leaf mitochondria. Journal of Experimental Botany 75, 917–934.
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Affiliation(s)
- Paul E Verslues
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11528, Taiwan
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2
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Mao Y, Seravalli J, Smith TG, Morton M, Tanner JJ, Becker DF. Evidence for Proline Catabolic Enzymes in the Metabolism of Thiazolidine Carboxylates. Biochemistry 2021; 60:3610-3620. [PMID: 34752700 DOI: 10.1021/acs.biochem.1c00625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thiazolidine carboxylates such as thiazolidine-4-carboxylate (T4C) and thiazolidine-2-carboxylate (T2C) are naturally occurring sulfur analogues of proline. These compounds have been observed to have both beneficial and toxic effects in cells. Given that proline dehydrogenase has been proposed to be a key enzyme in the oxidative metabolism of thioprolines, we characterized T4C and T2C as substrates of proline catabolic enzymes using proline utilization A (PutA), which is a bifunctional enzyme with proline dehydrogenase (PRODH) and l-glutamate-γ-semialdehyde dehydrogenase (GSALDH) activities. PutA is shown here to catalyze the FAD-dependent PRODH oxidation of both T4C and T2C with catalytic efficiencies significantly higher than with proline. Stopped-flow experiments also demonstrate that l-T4C and l-T2C reduce PutA-bound FAD at rates faster than proline. Unlike proline, however, oxidation of T4C and T2C does not generate a substrate for NAD+-dependent GSALDH. Instead, PutA/PRODH oxidation of T4C leads to cysteine formation, whereas oxidation of T2C generates an apparently stable Δ4-thiazoline-2-carboxylate species. Our results provide new insights into the metabolism of T2C and T4C.
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Affiliation(s)
- Yizi Mao
- Department of Biochemistry, Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Javier Seravalli
- Department of Biochemistry, Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Thomas G Smith
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Martha Morton
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - John J Tanner
- Departments of Biochemistry and Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Donald F Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, United States
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Fabro G, Cislaghi AP, Condat F, Deza Borau G, Alvarez ME. The N-terminal domain of Arabidopsis proline dehydrogenase affects enzymatic activity and protein oligomerization. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2020; 154:268-276. [PMID: 32574985 DOI: 10.1016/j.plaphy.2020.04.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 03/10/2020] [Accepted: 04/13/2020] [Indexed: 05/21/2023]
Abstract
Proline dehydrogenase (ProDH) is a flavoenzyme that catalyzes the oxidation of proline (Pro) into Δ1-pyrroline-5-carboxylate (P5C). In eukaryotes, ProDH coordinates with different Pro metabolism enzymes to control energy supply or stress responses signaling. Heterologous expression and crystallization of prokaryotic enzymes provided key data on their active center, folding capacity and oligomerization status. In contrast, eukaryotic ProDHs have not been crystallized so far, and their study as recombinant proteins remains limited. Plants contain two isoforms of ProDH with non-redundant functions. To contribute to the study of these enzymes, we describe the modeling, expression in E. coli, purification, and characterization of the Arabidopsis isoenzymes, AtProDH1 and AtProDH2. The 3D model suggested that both proteins adopt a distorted barrel structure (βα) with a cap formed by N-terminal α helices. The expression of two types of N-terminal deletion proteins indicated that this domain affected enzyme activity. Full-length enzymes had Km values similar to those of native proteins, whereas truncated proteins were inactive. Moreover, the first α helix proved to be necessary for AtProDH1 and AtProDH2 activities. Interestingly, both isoenzymes were able to oligomerize and this also required the first N-terminal α helix. Thus, we report the first insights into structure-function relationship of plant ProDHs demonstrating that the N-terminus, although not directly involved in catalysis, controls enzyme arrangement and activity. The resources generated here could be useful to analyze other plant ProDH features, such as its coordination with other enzymes, and differences between ProDH1 and ProDH2, providing new information on its effects on stress tolerance.
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Affiliation(s)
- Georgina Fabro
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET, Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina.
| | - Ana Paula Cislaghi
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET, Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina
| | - Félix Condat
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET, Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina
| | - Germán Deza Borau
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET, Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina
| | - María Elena Alvarez
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET, Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina.
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Lebreton S, Cabassa-Hourton C, Savouré A, Funck D, Forlani G. Appropriate Activity Assays Are Crucial for the Specific Determination of Proline Dehydrogenase and Pyrroline-5-Carboxylate Reductase Activities. FRONTIERS IN PLANT SCIENCE 2020; 11:602939. [PMID: 33424902 PMCID: PMC7785524 DOI: 10.3389/fpls.2020.602939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 12/03/2020] [Indexed: 05/04/2023]
Abstract
Accumulation of proline is a widespread plant response to a broad range of environmental stress conditions including salt and osmotic stress. Proline accumulation is achieved mainly by upregulation of proline biosynthesis in the cytosol and by inhibition of proline degradation in mitochondria. Changes in gene expression or activity levels of the two enzymes catalyzing the first reactions in these two pathways, namely pyrroline-5-carboxylate (P5C) synthetase and proline dehydrogenase (ProDH), are often used to assess the stress response of plants. The difficulty to isolate ProDH in active form has led several researchers to erroneously report proline-dependent NAD+ reduction at pH 10 as ProDH activity. We demonstrate that this activity is due to P5C reductase (P5CR), the second and last enzyme in proline biosynthesis, which works in the reverse direction at unphysiologically high pH. ProDH does not use NAD+ as electron acceptor but can be assayed with the artificial electron acceptor 2,6-dichlorophenolindophenol (DCPIP) after detergent-mediated solubilization or enrichment of mitochondria. Seemingly counter-intuitive results from previous publications can be explained in this way and our data highlight the importance of appropriate and specific assays for the detection of ProDH and P5CR activities in crude plant extracts.
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Affiliation(s)
- Sandrine Lebreton
- Sorbonne Université, UPEC, CNRS, IRD, INRAE, Institute of Ecology and Environmental Sciences—Paris, IEES, Paris, France
| | - Cécile Cabassa-Hourton
- Sorbonne Université, UPEC, CNRS, IRD, INRAE, Institute of Ecology and Environmental Sciences—Paris, IEES, Paris, France
| | - Arnould Savouré
- Sorbonne Université, UPEC, CNRS, IRD, INRAE, Institute of Ecology and Environmental Sciences—Paris, IEES, Paris, France
| | - Dietmar Funck
- Department of Biology, University of Konstanz, Konstanz, Germany
- *Correspondence: Dietmar Funck,
| | - Giuseppe Forlani
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
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Huijbers MME, Wu JW, Westphal AH, Berkel WJH. Dimerization of Proline Dehydrogenase from
Thermus thermophilus
Is Crucial for Its Thermostability. Biotechnol J 2019; 14:e1800540. [DOI: 10.1002/biot.201800540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/22/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Mieke M. E. Huijbers
- Laboratory of BiochemistryWageningen University & ResearchStippeneng 4, 6708 WE Wageningen The Netherlands
| | - Jenny W. Wu
- Laboratory of BiochemistryWageningen University & ResearchStippeneng 4, 6708 WE Wageningen The Netherlands
| | - Adrie H. Westphal
- Laboratory of BiochemistryWageningen University & ResearchStippeneng 4, 6708 WE Wageningen The Netherlands
| | - Willem J. H. Berkel
- Laboratory of BiochemistryWageningen University & ResearchStippeneng 4, 6708 WE Wageningen The Netherlands
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Christgen SL, Becker DF. Role of Proline in Pathogen and Host Interactions. Antioxid Redox Signal 2019; 30:683-709. [PMID: 29241353 PMCID: PMC6338583 DOI: 10.1089/ars.2017.7335] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/26/2017] [Accepted: 11/14/2017] [Indexed: 01/20/2023]
Abstract
SIGNIFICANCE Proline metabolism has complex roles in a variety of biological processes, including cell signaling, stress protection, and energy production. Proline also contributes to the pathogenesis of various disease-causing organisms. Understanding the mechanisms of how pathogens utilize proline is important for developing new strategies against infectious diseases. Recent Advances: The ability of pathogens to acquire amino acids is critical during infection. Besides protein biosynthesis, some amino acids, such as proline, serve as a carbon, nitrogen, or energy source in bacterial and protozoa pathogens. The role of proline during infection depends on the physiology of the host/pathogen interactions. Some pathogens rely on proline as a critical respiratory substrate, whereas others exploit proline for stress protection. CRITICAL ISSUES Disruption of proline metabolism and uptake has been shown to significantly attenuate virulence of certain pathogens, whereas in other pathogens the importance of proline during infection is not known. Inhibiting proline metabolism and transport may be a useful therapeutic strategy against some pathogens. Developing specific inhibitors to avoid off-target effects in the host, however, will be challenging. Also, potential treatments that target proline metabolism should consider the impact on intracellular levels of Δ1-pyrroline-5-carboxylate, a metabolite intermediate that can have opposing effects on pathogenesis. FUTURE DIRECTIONS Further characterization of how proline metabolism is regulated during infection would provide new insights into the role of proline in pathogenesis. Biochemical and structural characterization of proline metabolic enzymes from different pathogens could lead to new tools for exploring proline metabolism during infection and possibly new therapeutic compounds.
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Affiliation(s)
- Shelbi L. Christgen
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
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Abstract
SIGNIFICANCE Proline catabolism refers to the 4-electron oxidation of proline to glutamate catalyzed by the enzymes proline dehydrogenase (PRODH) and l-glutamate γ-semialdehyde dehydrogenase (GSALDH, or ALDH4A1). These enzymes and the intermediate metabolites of the pathway have been implicated in tumor growth and suppression, metastasis, hyperprolinemia metabolic disorders, schizophrenia susceptibility, life span extension, and pathogen virulence and survival. In some bacteria, PRODH and GSALDH are combined into a bifunctional enzyme known as proline utilization A (PutA). PutAs are not only virulence factors in some pathogenic bacteria but also fascinating systems for studying the coordination of metabolic enzymes via substrate channeling. Recent Advances: The past decade has seen an explosion of structural data for proline catabolic enzymes. This review surveys these structures, emphasizing protein folds, substrate recognition, oligomerization, kinetic mechanisms, and substrate channeling in PutA. CRITICAL ISSUES Major unsolved structural targets include eukaryotic PRODH, the complex between monofunctional PRODH and monofunctional GSALDH, and the largest of all PutAs, trifunctional PutA. The structural basis of PutA-membrane association is poorly understood. Fundamental aspects of substrate channeling in PutA remain unknown, such as the identity of the channeled intermediate, how the tunnel system is activated, and the roles of ancillary tunnels. FUTURE DIRECTIONS New approaches are needed to study the molecular and in vivo mechanisms of substrate channeling. With the discovery of the proline cycle driving tumor growth and metastasis, the development of inhibitors of proline metabolic enzymes has emerged as an exciting new direction. Structural biology will be important in these endeavors.
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Affiliation(s)
- John J Tanner
- 1 Department of Biochemistry and University of Missouri-Columbia , Columbia, Missouri.,2 Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri
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Abstract
SIGNIFICANCE It is increasingly clear that proline metabolism plays an important role in metabolic reprogramming, not only in cancer but also in related fields such as aging, senescence, and development. Although first focused on proline catabolism, recent studies from a number of laboratories have emphasized the regulatory effects of proline synthesis and proline cycling. Recent Advances: Although proline dehydrogenase/proline oxidase (PRODH/POX) has been known as a tumor protein 53 (P53)-activated source of redox signaling for initiating apoptosis and autophagy, senescence has been added to the responses. On the biosynthetic side, two well-recognized oncogenes, c-MYC and phosphoinositide 3-kinase (PI3K), markedly upregulate enzymes of proline synthesis; mechanisms affected include augmented redox cycling and maintenance of pyridine nucleotides. The reprogramming has been shown to shift in clonogenesis and/or metastasis. CRITICAL ISSUES Although PRODH/POX generates reactive oxygen species (ROS) for signaling, the cellular endpoint is variable and dependent on metabolic context; the switches for these responses remain unknown. On the synthetic side, the enzymes require more complete characterization in various cancers, and demonstration of coupling of proline metabolites to other pathways may require studies of protein-protein interactions, membrane transporters, and shuttles. FUTURE DIRECTIONS The proline metabolic axis can serve as a scaffold on which a variety of regulatory mechanisms are integrated. Once understood as a central mechanism in cancer metabolism, proline metabolism may be a good target for adjunctive cancer therapy.
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Affiliation(s)
- James M Phang
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute at Frederick, NIH , Frederick, Maryland
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9
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“Alternative” fuels contributing to mitochondrial electron transport: Importance of non-classical pathways in the diversity of animal metabolism. Comp Biochem Physiol B Biochem Mol Biol 2018; 224:185-194. [DOI: 10.1016/j.cbpb.2017.11.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 11/08/2017] [Accepted: 11/10/2017] [Indexed: 12/19/2022]
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Abstract
Interest in how proline contributes to cancer biology is expanding because of the emerging role of a novel proline metabolic cycle in cancer cell survival, proliferation, and metastasis. Proline biosynthesis and degradation involve the shared intermediate Δ1-pyrroline-5-carboxylate (P5C), which forms l-glutamate-γ-semialdehyde (GSAL) in a reversible non-enzymatic reaction. Proline is synthesized from glutamate or ornithine through GSAL/P5C, which is reduced to proline by P5C reductase (PYCR) in a NAD(P)H-dependent reaction. The degradation of proline occurs in the mitochondrion and involves two oxidative steps catalyzed by proline dehydrogenase (PRODH) and GSAL dehydrogenase (GSALDH). PRODH is a flavin-dependent enzyme that couples proline oxidation with reduction of membrane-bound quinone, while GSALDH catalyzes the NAD+-dependent oxidation of GSAL to glutamate. PRODH and PYCR form a metabolic relationship known as the proline-P5C cycle, a novel pathway that impacts cellular growth and death pathways. The proline-P5C cycle has been implicated in supporting ATP production, protein and nucleotide synthesis, anaplerosis, and redox homeostasis in cancer cells. This Perspective details the structures and reaction mechanisms of PRODH and PYCR and the role of the proline-P5C cycle in cancer metabolism. A major challenge in the field is to discover inhibitors that specifically target PRODH and PYCR isoforms for use as tools for studying proline metabolism and the functions of the proline-P5C cycle in cancer. These molecular probes could also serve as lead compounds in cancer drug discovery targeting the proline-P5C cycle.
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Affiliation(s)
- John J. Tanner
- Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65211, United States
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211, United States
| | - Sarah-Maria Fendt
- Laboratory of Cellular Metabolism and Metabolic Regulation, VIB Center for Cancer Biology, VIB, Herestraat 49, 3000 Leuven, Belgium
- Laboratory of Cellular Metabolism and Metabolic Regulation, Department of Oncology, KU Leuven and Leuven Cancer Institute (LKI), Herestraat 49, 3000 Leuven, Belgium
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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Christgen SL, Zhu W, Sanyal N, Bibi B, Tanner JJ, Becker DF. Discovery of the Membrane Binding Domain in Trifunctional Proline Utilization A. Biochemistry 2017; 56:6292-6303. [PMID: 29090935 PMCID: PMC6044449 DOI: 10.1021/acs.biochem.7b01008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Escherichia coli proline utilization A (EcPutA) is the archetype of trifunctional PutA flavoproteins, which function both as regulators of the proline utilization operon and bifunctional enzymes that catalyze the four-electron oxidation of proline to glutamate. EcPutA shifts from a self-regulating transcriptional repressor to a bifunctional enzyme in a process known as functional switching. The flavin redox state dictates the function of EcPutA. Upon proline oxidation, the flavin becomes reduced, triggering a conformational change that causes EcPutA to dissociate from the put regulon and bind to the cellular membrane. Major structure/function domains of EcPutA have been characterized, including the DNA-binding domain, proline dehydrogenase (PRODH) and l-glutamate-γ-semialdehyde dehydrogenase catalytic domains, and an aldehyde dehydrogenase superfamily fold domain. Still lacking is an understanding of the membrane-binding domain, which is essential for EcPutA catalytic turnover and functional switching. Here, we provide evidence for a conserved C-terminal motif (CCM) in EcPutA having a critical role in membrane binding. Deletion of the CCM or replacement of hydrophobic residues with negatively charged residues within the CCM impairs EcPutA functional and physical membrane association. Furthermore, cell-based transcription assays and limited proteolysis indicate that the CCM is essential for functional switching. Using fluorescence resonance energy transfer involving dansyl-labeled liposomes, residues in the α-domain are also implicated in membrane binding. Taken together, these experiments suggest that the CCM and α-domain converge to form a membrane-binding interface near the PRODH domain. The discovery of the membrane-binding region will assist efforts to define flavin redox signaling pathways responsible for EcPutA functional switching.
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Affiliation(s)
- Shelbi L. Christgen
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Weidong Zhu
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Nikhilesh Sanyal
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Bushra Bibi
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - John J. Tanner
- Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65211, United States
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211, United States
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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Liu LK, Becker DF, Tanner JJ. Structure, function, and mechanism of proline utilization A (PutA). Arch Biochem Biophys 2017; 632:142-157. [PMID: 28712849 DOI: 10.1016/j.abb.2017.07.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 01/13/2023]
Abstract
Proline has important roles in multiple biological processes such as cellular bioenergetics, cell growth, oxidative and osmotic stress response, protein folding and stability, and redox signaling. The proline catabolic pathway, which forms glutamate, enables organisms to utilize proline as a carbon, nitrogen, and energy source. FAD-dependent proline dehydrogenase (PRODH) and NAD+-dependent glutamate semialdehyde dehydrogenase (GSALDH) convert proline to glutamate in two sequential oxidative steps. Depletion of PRODH and GSALDH in humans leads to hyperprolinemia, which is associated with mental disorders such as schizophrenia. Also, some pathogens require proline catabolism for virulence. A unique aspect of proline catabolism is the multifunctional proline utilization A (PutA) enzyme found in Gram-negative bacteria. PutA is a large (>1000 residues) bifunctional enzyme that combines PRODH and GSALDH activities into one polypeptide chain. In addition, some PutAs function as a DNA-binding transcriptional repressor of proline utilization genes. This review describes several attributes of PutA that make it a remarkable flavoenzyme: (1) diversity of oligomeric state and quaternary structure; (2) substrate channeling and enzyme hysteresis; (3) DNA-binding activity and transcriptional repressor function; and (4) flavin redox dependent changes in subcellular location and function in response to proline (functional switching).
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Affiliation(s)
- Li-Kai Liu
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, United States
| | - Donald F Becker
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588-0664, United States.
| | - John J Tanner
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, United States; Department of Chemistry, University of Missouri, Columbia, MO, 65211, United States.
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Natarajan SK, Muthukrishnan E, Khalimonchuk O, Mott JL, Becker DF. Evidence for Pipecolate Oxidase in Mediating Protection Against Hydrogen Peroxide Stress. J Cell Biochem 2016; 118:1678-1688. [PMID: 27922192 DOI: 10.1002/jcb.25825] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 12/02/2016] [Indexed: 01/16/2023]
Abstract
Pipecolate, an intermediate of the lysine catabolic pathway, is oxidized to Δ1 -piperideine-6-carboxylate (P6C) by the flavoenzyme l-pipecolate oxidase (PIPOX). P6C spontaneously hydrolyzes to generate α-aminoadipate semialdehyde, which is then converted into α-aminoadipate acid by α-aminoadipatesemialdehyde dehydrogenase. l-pipecolate was previously reported to protect mammalian cells against oxidative stress. Here, we examined whether PIPOX is involved in the mechanism of pipecolate stress protection. Knockdown of PIPOX by small interference RNA abolished pipecolate protection against hydrogen peroxide-induced cell death in HEK293 cells suggesting a critical role for PIPOX. Subcellular fractionation analysis showed that PIPOX is localized in the mitochondria of HEK293 cells consistent with its role in lysine catabolism. Signaling pathways potentially involved in pipecolate protection were explored by treating cells with small molecule inhibitors. Inhibition of both mTORC1 and mTORC2 kinase complexes or inhibition of Akt kinase alone blocked pipecolate protection suggesting the involvement of these signaling pathways. Phosphorylation of the Akt downstream target, forkhead transcription factor O3 (FoxO3), was also significantly increased in cells treated with pipecolate, further implicating Akt in the protective mechanism and revealing FoxO3 inhibition as a potentially key step. The results presented here demonstrate that pipecolate metabolism can influence cell signaling during oxidative stress to promote cell survival and suggest that the mechanism of pipecolate protection parallels that of proline, which is also metabolized in the mitochondria. J. Cell. Biochem. 118: 1678-1688, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Sathish Kumar Natarajan
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588.,Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, 68583
| | - Ezhumalai Muthukrishnan
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, 68583
| | - Oleh Khalimonchuk
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588
| | - Justin L Mott
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, 68198
| | - Donald F Becker
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588
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Proteomic and functional analysis of proline dehydrogenase 1 link proline catabolism to mitochondrial electron transport in Arabidopsis thaliana. Biochem J 2016; 473:2623-34. [PMID: 27303048 DOI: 10.1042/bcj20160314] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 06/14/2016] [Indexed: 11/17/2022]
Abstract
Proline accumulates in many plant species in response to environmental stresses. Upon relief from stress, proline is rapidly oxidized in mitochondria by proline dehydrogenase (ProDH) and then by pyrroline-5-carboxylate dehydrogenase (P5CDH). Two ProDH genes have been identified in the genome of the model plant Arabidopsis thaliana To gain a better understanding of ProDH1 functions in mitochondria, proteomic analysis was performed. ProDH1 polypeptides were identified in Arabidopsis mitochondria by immunoblotting gels after 2D blue native (BN)-SDS/PAGE, probing them with an anti-ProDH antibody and analysing protein spots by MS. The 2D gels showed that ProDH1 forms part of a low-molecular-mass (70-140 kDa) complex in the mitochondrial membrane. To evaluate the contribution of each isoform to proline oxidation, mitochondria were isolated from wild-type (WT) and prodh1, prodh2, prodh1prodh2 and p5cdh mutants. ProDH activity was high for genotypes in which ProDH, most likely ProDH1, was strongly induced by proline. Respiratory measurements indicate that ProDH1 has a role in oxidizing excess proline and transferring electrons to the respiratory chain.
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Hancock CN, Liu W, Alvord WG, Phang JM. Co-regulation of mitochondrial respiration by proline dehydrogenase/oxidase and succinate. Amino Acids 2015; 48:859-872. [PMID: 26660760 PMCID: PMC4752965 DOI: 10.1007/s00726-015-2134-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 11/05/2015] [Indexed: 02/03/2023]
Abstract
Proline dehydrogenase/oxidase (PRODH/POX) is a mitochondrial protein critical to multiple stress pathways. Because of the roles of PRODH/POX in signaling, and its shared localization to the mitochondrial inner membrane with the electron transport chain (ETC), we investigated whether there was a direct relationship between PRODH/POX and regulation of the ETC. We found that PRODH/POX binds directly to CoQ1 and that CoQ1-dependent PRODH/POX activity required functional Complex III and Complex IV. PRODH/POX supported respiration in living cells during nutrient stress; however, expression of PRODH/POX resulted in an overall decrease in respiratory fitness. Effects on respiratory fitness were inhibited by DHP and NAC, indicating that these effects were mediated by PRODH/POX-dependent reactive oxygen species (ROS) generation. PRODH/POX expression resulted in a dose-dependent down-regulation of Complexes I–IV of the ETC, and this effect was also mitigated by the addition of DHP and NAC. We found that succinate was an uncompetitive inhibitor of PRODH/POX activity, inhibited ROS generation by PRODH/POX, and alleviated PRODH/POX effects on respiratory fitness. The findings demonstrate novel cross-talk between proline and succinate respiration in vivo and provide mechanistic insights into observations from previous animal studies. Our results suggest a potential regulatory loop between PRODH/POX and succinate in regulation of mitochondrial respiration.
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Affiliation(s)
- Chad N Hancock
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, NCI-Frederick, 1050 Boyles Street, Bldg. 538, Rm. 144, Frederick, MD, 21702-1201, USA.
| | - Wei Liu
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, NCI-Frederick, 1050 Boyles Street, Bldg. 538, Rm. 144, Frederick, MD, 21702-1201, USA
| | - W Gregory Alvord
- Data Management Services, National Cancer Institute at Frederick, Frederick, MD, 21702, USA
| | - James M Phang
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, NCI-Frederick, 1050 Boyles Street, Bldg. 538, Rm. 144, Frederick, MD, 21702-1201, USA.
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Hyperprolinemia in Type 2 Glutaric Aciduria and MADD-Like Profiles. JIMD Rep 2015; 27:39-45. [PMID: 26409463 DOI: 10.1007/8904_2015_481] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 06/29/2015] [Accepted: 07/02/2015] [Indexed: 12/13/2022] Open
Abstract
Classical neonatal-onset glutaric aciduria type 2 (MAD deficiency) is a severe disorder of mitochondrial fatty acid oxidation associated with poor survival. Secondary dysfunction of acyl-CoA dehydrogenases may result from deficiency for riboflavin transporters, leading to severe disorders that, nevertheless, are treatable by riboflavin supplementation. In the last 10 years, we identified nine newborns with biochemical features consistent with MAD deficiency, only four of whom survived past the neonatal period. A likely iatrogenic cause of riboflavin deficiency was found in two premature newborns having parenteral nutrition, one of whom recovered upon multivitamin supplementation, whereas the other died before diagnosis. Four other patients had demonstrated mutations involving ETF or ETF-DH flavoproteins, whereas the remaining three patients presumably had secondary deficiencies of unknown mechanism. Interestingly, six newborns among the seven tested for plasma amino acids had pronounced hyperprolinemia. In one case, because the initial diagnostic workup did not include organic acids and acylcarnitine profiling, clinical presentation and hyperprolinemia suggested the diagnosis. Analysis of our full cohort of >50,000 samples from >30,000 patients suggests that the proline/alanine ratio may be a good marker of MAD deficiency and could contribute to a more effective management of the treatable forms.
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Proline dehydrogenase 2 (PRODH2) is a hydroxyproline dehydrogenase (HYPDH) and molecular target for treating primary hyperoxaluria. Biochem J 2015; 466:273-81. [PMID: 25697095 DOI: 10.1042/bj20141159] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The primary hyperoxalurias (PH), types 1-3, are disorders of glyoxylate metabolism that result in increased oxalate production and calcium oxalate stone formation. The breakdown of trans-4-hydroxy-L-proline (Hyp) from endogenous and dietary sources of collagen makes a significant contribution to the cellular glyoxylate pool. Proline dehydrogenase 2 (PRODH2), historically known as hydroxyproline oxidase, is the first step in the hydroxyproline catabolic pathway and represents a drug target to reduce the glyoxylate and oxalate burden of PH patients. This study is the first report of the expression, purification, and biochemical characterization of human PRODH2. Evaluation of a panel of N-terminal and C-terminal truncation variants indicated that residues 157-515 contain the catalytic core with one FAD molecule. The 12-fold higher k(cat)/K(m) value of 0.93 M⁻¹·s⁻¹ for Hyp over Pro demonstrates the preference for Hyp as substrate. Moreover, an anaerobic titration determined a K(d) value of 125 μM for Hyp, a value ~1600-fold lower than the K(m) value. A survey of ubiquinone analogues revealed that menadione, duroquinone, and CoQ₁ reacted more efficiently than oxygen as the terminal electron acceptor during catalysis. Taken together, these data and the slow reactivity with sodium sulfite support that PRODH2 functions as a dehydrogenase and most likely utilizes CoQ₁₀ as the terminal electron acceptor in vivo. Thus, we propose that the name of PRODH2 be changed to hydroxyproline dehydrogenase (HYPDH). Three Hyp analogues were also identified to inhibit the activity of HYPDH, representing the first steps toward the development of a novel approach to treat all forms of PH.
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Huijbers MM, van Berkel WJ. High yields of activeThermus thermophilusproline dehydrogenase are obtained using maltose-binding protein as a solubility tag. Biotechnol J 2015; 10:395-403. [DOI: 10.1002/biot.201400229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/24/2014] [Accepted: 12/22/2014] [Indexed: 12/19/2022]
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19
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Qamar A, Mysore KS, Senthil-Kumar M. Role of proline and pyrroline-5-carboxylate metabolism in plant defense against invading pathogens. FRONTIERS IN PLANT SCIENCE 2015; 6:503. [PMID: 26217357 PMCID: PMC4491715 DOI: 10.3389/fpls.2015.00503] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 06/22/2015] [Indexed: 05/18/2023]
Abstract
Pyrroline-5-carboxylate (P5C) is an intermediate product of both proline biosynthesis and catabolism. Recent evidences indicate that proline-P5C metabolism is tightly regulated in plants, especially during pathogen infection and abiotic stress. However, role of P5C and its metabolism in plants has not yet been fully understood. Studies indicate that P5C synthesized in mitochondria has a role in both resistance (R)-gene-mediated and non-host resistance against invading pathogens. Proline dehydrogenase and delta-ornithine amino transferase-encoding genes, both involved in P5C synthesis in mitochondria are implicated in defense response of Nicotiana benthamiana and Arabidopsis thaliana against bacterial pathogens. Such defense response is proposed to involve salicylic acid-dependent pathway, reactive oxygen species (ROS) and hypersensitive response (HR)-associated cell death. Recently HR, a form of programmed cell death (PCD), has been proposed to be induced by changes in mitochondrial P5C synthesis or the increase in P5C levels per se in plants inoculated with either a host pathogen carrying suitable avirulent (Avr) gene or a non-host pathogen. Consistently, A. thaliana mutant plants deficient in P5C catabolism showed HR like cell death when grown in external P5C or proline supplemented medium. Similarly, yeast and plant cells under oxidative stress were shown to increase ROS production and PCD due to increase in P5C levels. Similar mechanism has also been reported as one of the triggers for apoptosis in mammalian cells. This review critically analyzes results from various studies and enumerates the pathways for regulation of P5C levels in the plant cell, especially in mitochondria, during pathogen infection. Further, mechanisms regulating P5C- mediated defense responses, namely HR are outlined. This review also provides new insights into the differential role of proline-P5C metabolism in plants exposed to pathogen infection.
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Affiliation(s)
- Aarzoo Qamar
- National Institute of Plant Genome ResearchNew Delhi, India
| | | | - Muthappa Senthil-Kumar
- National Institute of Plant Genome ResearchNew Delhi, India
- *Correspondence: Muthappa Senthil-Kumar, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, P. O. Box 10531, New Delhi 110067, India,
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20
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Goncalves RLS, Rothschild DE, Quinlan CL, Scott GK, Benz CC, Brand MD. Sources of superoxide/H2O2 during mitochondrial proline oxidation. Redox Biol 2014; 2:901-9. [PMID: 25184115 PMCID: PMC4143814 DOI: 10.1016/j.redox.2014.07.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 07/07/2014] [Indexed: 12/28/2022] Open
Abstract
p53 Inducible gene 6 (PIG6) encodes mitochondrial proline dehydrogenase (PRODH) and is up-regulated several fold upon p53 activation. Proline dehydrogenase is proposed to generate radicals that contribute to cancer cell apoptosis. However, there are at least 10 mitochondrial sites that can produce superoxide and/or H2O2, and it is unclear whether proline dehydrogenase generates these species directly, or instead drives production by other sites. Amongst six cancer cell lines, ZR75-30 human breast cancer cells had the highest basal proline dehydrogenase levels, and mitochondria isolated from ZR75-30 cells consumed oxygen and produced H2O2 with proline as sole substrate. Insects use proline oxidation to fuel flight, and mitochondria isolated from Drosophila melanogaster were even more active with proline as sole substrate than ZR75-30 mitochondria. Using mitochondria from these two models we identified the sites involved in formation of superoxide/H2O2 during proline oxidation. In mitochondria from Drosophila the main sites were respiratory complexes I and II. In mitochondria from ZR75-30 breast cancer cells the main sites were complex I and the oxoglutarate dehydrogenase complex. Even with combinations of substrates and respiratory chain inhibitors designed to minimize the contributions of other sites and maximize any superoxide/H2O2 production from proline dehydrogenase itself, there was no significant direct contribution of proline dehydrogenase to the observed H2O2 production. Thus proline oxidation by proline dehydrogenase drives superoxide/H2O2 production, but it does so mainly or exclusively by providing anaplerotic carbon for other mitochondrial dehydrogenases and not by producing superoxide/H2O2 directly. Proline dehydrogenase is thought to produce reactive oxygen species (ROS) in cancer cells and to promote apoptosis. Isolated mitochondria from Drosophila melanogaster and from a human breast cancer cell line oxidize proline producing superoxide/H2O2 at measurable rates. Proline oxidation drives superoxide/H2O2 production indirectly at other sites and it is unlikely that proline dehydrogenase produces superoxide/H2O2 itself. In Drosophila, superoxide/H2O2 arises from sites IF and IIF (the flavin sites from complexes I and II, respectively). In the breast cancer cell line the main sites are IF and OF (from the oxoglutarate dehydrogenase complex).
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Key Words
- A5, atpenin A5
- AT, aminotransferase
- Asp, asparate
- Cancer cell mitochondria
- Drosophila
- Electron transport chain
- GDH, glutamate dehydrogenase
- GSA, glutamic semi-aldehyde
- Hydrogen peroxide
- IF, flavin of complex I
- IIF, flavin of complex II
- IIIQo, quinone binding site on the outer/cytosolic face of complex III
- OF, Flavin of the oxoglutarate dehydrogenase complex
- OGDH, 2-oxoglutarate dehydrogenase complex
- Oxa, oxaloacetate
- P5C, Δ1-pyrroline-5-carboxylate
- PIG6, proline dehydrogenase inducible gene 6
- PRODH, proline dehydrogenase
- Proline dehydrogenase (PRODH)
- ROS, reactive oxygen species
- Reactive oxygen species
- SCS, succinyl-CoA synthase
- Superoxide
- TCA, tricarboxylic acid
- oAB, o-aminobenzaldehyde
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Affiliation(s)
| | | | | | - Gary K Scott
- Buck Institute for Research on Aging, Novato, CA 94945, USA
| | | | - Martin D Brand
- Buck Institute for Research on Aging, Novato, CA 94945, USA
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Wadhawan S, Gautam S, Sharma A. Involvement of proline oxidase (PutA) in programmed cell death of Xanthomonas. PLoS One 2014; 9:e96423. [PMID: 24788936 PMCID: PMC4006831 DOI: 10.1371/journal.pone.0096423] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/06/2014] [Indexed: 12/19/2022] Open
Abstract
Xanthomonas campestris strains have been reported to undergo programmed cell death (PCD) in a protein rich medium. Protein hydrolysates used in media such as nutrient broth comprise of casein digest with abundance of proline and glutamate. In the current study, X. campestris pv. campestris (Xcc) cells displayed PCD when grown in PCD inducing medium (PIM) containing casein tryptic digest. This PCD was also observed in PCD non-inducing carbohydrate rich medium (PNIM) fortified with either proline or proline along with glutamate. Surprisingly, no PCD was noticed in PNIM fortified with glutamate alone. Differential role of proline or glutamate in inducing PCD in Xcc cells growing in PNIM was studied. It was found that an intermediate product of this oxidation was involved in initiation of PCD. Proline oxidase also called as proline utilization A (PutA), catalyzes the two step oxidation of proline to glutamate. Interestingly, higher PutA activity was noticed in cells growing in PIM, and PCD was found to be inhibited by tetrahydro-2-furoic acid, a competitive inhibitor of this enzyme. Further, PCD was abolished in Xcc ΔputA strain generated using a pKNOCK suicide plasmid, and restored in Xcc ΔputA strain carrying functional PutA in a plasmid vector. Xanthomonas cells growing in PIM also displayed increased generation of ROS, as well as cell filamentation (a probable indication of SOS response). These filamented cells also displayed enhanced caspase-3-like activity during in situ labeling using a fluorescent tagged caspase-3 inhibitor (FITC-DEVD-FMK). The extent of PCD associated markers such as DNA damage, phosphatidylserine externalization and membrane depolarization were found to be significantly enhanced in wild type cells, but drastically reduced in Xcc ΔputA cells. These findings thus establish the role of PutA mediated proline oxidation in regulating death in stressed Xanthomonas cells.
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Affiliation(s)
- Surbhi Wadhawan
- Food Technology Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Satyendra Gautam
- Food Technology Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Arun Sharma
- Food Technology Division, Bhabha Atomic Research Centre, Mumbai, India
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22
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Pemberton TA, Srivastava D, Sanyal N, Henzl MT, Becker DF, Tanner JJ. Structural studies of yeast Δ(1)-pyrroline-5-carboxylate dehydrogenase (ALDH4A1): active site flexibility and oligomeric state. Biochemistry 2014; 53:1350-9. [PMID: 24502590 PMCID: PMC3954644 DOI: 10.1021/bi500048b] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
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The proline catabolic enzyme Δ1-pyrroline-5-carboxylate
dehydrogenase (ALDH4A1) catalyzes the NAD+-dependent oxidation
of γ-glutamate semialdehyde to l-glutamate. In Saccharomyces cerevisiae, ALDH4A1 is encoded by the PUT2 gene and known as Put2p. Here we report the steady-state
kinetic parameters of the purified recombinant enzyme, two crystal
structures of Put2p, and the determination of the oligomeric state
and quaternary structure from small-angle X-ray scattering and sedimentation
velocity. Using Δ1-pyrroline-5-carboxylate as the
substrate, catalytic parameters kcat and Km were determined to be 1.5 s–1 and 104 μM, respectively, with a catalytic efficiency of 14000
M–1 s–1. Although Put2p exhibits
the expected aldehyde dehydrogenase superfamily fold, a large portion
of the active site is disordered in the crystal structure. Electron
density for the 23-residue aldehyde substrate-binding loop is absent,
implying substantial conformational flexibility in solution. We furthermore
report a new crystal form of human ALDH4A1 (42% identical to Put2p)
that also shows disorder in this loop. The crystal structures provide
evidence of multiple active site conformations in the substrate-free
form of the enzyme, which is consistent with a conformational selection
mechanism of substrate binding. We also show that Put2p forms a trimer-of-dimers
hexamer in solution. This result is unexpected because human ALDH4A1
is dimeric, whereas some bacterial ALDH4A1s are hexameric. Thus, global
sequence identity and domain of life are poor predictors of the oligomeric
states of ALDH4A1. Mutation of a single Trp residue that forms knob-in-hole
interactions across the dimer–dimer interface abrogates hexamer
formation, suggesting that this residue is the center of a protein–protein
association hot spot.
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Affiliation(s)
- Travis A Pemberton
- Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri 65211, United States
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23
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Sieg AG, Trotter PJ. Differential contribution of the proline and glutamine pathways to glutamate biosynthesis and nitrogen assimilation in yeast lacking glutamate dehydrogenase. Microbiol Res 2014; 169:709-16. [PMID: 24629525 DOI: 10.1016/j.micres.2014.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 02/03/2014] [Accepted: 02/10/2014] [Indexed: 11/16/2022]
Abstract
In Saccharomyces cerevisiae, the glutamate dehydrogenase (GDH) enzymes play a pivotal role in glutamate biosynthesis and nitrogen assimilation. It has been proposed that, in GDH-deficient yeast, either the proline utilization (PUT) or the glutamine synthetase-glutamate synthase (GS/GOGAT) pathway serves as the alternative pathway for glutamate production and nitrogen assimilation to the exclusion of the other. Using a gdh-null mutant (gdh1Δ2Δ3Δ), this ambiguity was addressed using a combination of growth studies and pathway-specific enzyme assays on a variety of nitrogen sources (ammonia, glutamine, proline and urea). The GDH-null mutant was viable on all nitrogen sources tested, confirming that alternate pathways for nitrogen assimilation exist in the gdh-null strain. Enzyme assays point to GS/GOGAT as the primary alternative pathway on the preferred nitrogen sources ammonia and glutamine, whereas growth on proline required both the PUT and GS/GOGAT pathways. In contrast, growth on glucose-urea media elicited a decrease in GOGAT activity along with an increase in activity of the PUT pathway specific enzyme Δ(1)-pyrroline-5-carboxylate dehydrogenase (P5CDH). Together, these results suggest the alternative pathway for nitrogen assimilation in strains lacking the preferred GDH-dependent route is nitrogen source dependent and that neither GS/GOGAT nor PUT serves as the sole compensatory pathway.
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Affiliation(s)
- Alex G Sieg
- Guehler Biochemistry Laboratory, Department of Chemistry, Augustana College, 639-38th Street, Rock Island, IL 61201, United States
| | - Pamela J Trotter
- Guehler Biochemistry Laboratory, Department of Chemistry, Augustana College, 639-38th Street, Rock Island, IL 61201, United States.
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24
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Orellana M, Aceituno FF, Slater AW, Almonacid LI, Melo F, Agosin E. Metabolic and transcriptomic response of the wine yeast Saccharomyces cerevisiae strain EC1118 after an oxygen impulse under carbon-sufficient, nitrogen-limited fermentative conditions. FEMS Yeast Res 2014; 14:412-24. [PMID: 24387769 DOI: 10.1111/1567-1364.12135] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 12/09/2013] [Accepted: 12/29/2013] [Indexed: 11/27/2022] Open
Abstract
During alcoholic fermentation, Saccharomyces cerevisiae is exposed to continuously changing environmental conditions, such as decreasing sugar and increasing ethanol concentrations. Oxygen, a critical nutrient to avoid stuck and sluggish fermentations, is only discretely available throughout the process after pump-over operation. In this work, we studied the physiological response of the wine yeast S. cerevisiae strain EC1118 to a sudden increase in dissolved oxygen, simulating pump-over operation. With this aim, an impulse of dissolved oxygen was added to carbon-sufficient, nitrogen-limited anaerobic continuous cultures. Results showed that genes related to mitochondrial respiration, ergosterol biosynthesis, and oxidative stress, among other metabolic pathways, were induced after the oxygen impulse. On the other hand, mannoprotein coding genes were repressed. The changes in the expression of these genes are coordinated responses that share common elements at the level of transcriptional regulation. Beneficial and detrimental effects of these physiological processes on wine quality highlight the dual role of oxygen in 'making or breaking wines'. These findings will facilitate the development of oxygen addition strategies to optimize yeast performance in industrial fermentations.
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Affiliation(s)
- Marcelo Orellana
- Department of Chemical and Bioprocess Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Macul, Santiago, Chile
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25
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Abstract
SIGNIFICANCE The imino acid proline is utilized by different organisms to offset cellular imbalances caused by environmental stress. The wide use in nature of proline as a stress adaptor molecule indicates that proline has a fundamental biological role in stress response. Understanding the mechanisms by which proline enhances abiotic/biotic stress response will facilitate agricultural crop research and improve human health. RECENT ADVANCES It is now recognized that proline metabolism propels cellular signaling processes that promote cellular apoptosis or survival. Studies have shown that proline metabolism influences signaling pathways by increasing reactive oxygen species (ROS) formation in the mitochondria via the electron transport chain. Enhanced ROS production due to proline metabolism has been implicated in the hypersensitive response in plants, lifespan extension in worms, and apoptosis, tumor suppression, and cell survival in animals. CRITICAL ISSUES The ability of proline to influence disparate cellular outcomes may be governed by ROS levels generated in the mitochondria. Defining the threshold at which proline metabolic enzyme expression switches from inducing survival pathways to cellular apoptosis would provide molecular insights into cellular redox regulation by proline. Are ROS the only mediators of proline metabolic signaling or are other factors involved? FUTURE DIRECTIONS New evidence suggests that proline biosynthesis enzymes interact with redox proteins such as thioredoxin. An important future pursuit will be to identify other interacting partners of proline metabolic enzymes to uncover novel regulatory and signaling networks of cellular stress response.
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Affiliation(s)
- Xinwen Liang
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
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26
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Proline dehydrogenase regulates redox state and respiratory metabolism in Trypanosoma cruzi. PLoS One 2013; 8:e69419. [PMID: 23894476 PMCID: PMC3718742 DOI: 10.1371/journal.pone.0069419] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 06/10/2013] [Indexed: 11/19/2022] Open
Abstract
Over the past three decades, L-proline has become recognized as an important metabolite for trypanosomatids. It is involved in a number of key processes, including energy metabolism, resistance to oxidative and nutritional stress and osmoregulation. In addition, this amino acid supports critical parasite life cycle processes by acting as an energy source, thus enabling host-cell invasion by the parasite and subsequent parasite differentiation. In this paper, we demonstrate that L-proline is oxidized to Δ(1)-pyrroline-5-carboxylate (P5C) by the enzyme proline dehydrogenase (TcPRODH, E.C. 1.5.99.8) localized in Trypanosoma cruzi mitochondria. When expressed in its active form in Escherichia coli, TcPRODH exhibits a Km of 16.58±1.69 µM and a Vmax of 66±2 nmol/min mg. Furthermore, we demonstrate that TcPRODH is a FAD-dependent dimeric state protein. TcPRODH mRNA and protein expression are strongly upregulated in the intracellular epimastigote, a stage which requires an external supply of proline. In addition, when Saccharomyces cerevisiae null mutants for this gene (PUT1) were complemented with the TcPRODH gene, diminished free intracellular proline levels and an enhanced sensitivity to oxidative stress in comparison to the null mutant were observed, supporting the hypothesis that free proline accumulation constitutes a defense against oxidative imbalance. Finally, we show that proline oxidation increases cytochrome c oxidase activity in mitochondrial vesicles. Overall, these results demonstrate that TcPRODH is involved in proline-dependant cytoprotection during periods of oxidative imbalance and also shed light on the participation of proline in energy metabolism, which drives critical processes of the T. cruzi life cycle.
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27
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Pallotta ML. L-Proline uptake in Saccharomyces cerevisiae mitochondria can contribute to bioenergetics during nutrient stress as alternative mitochondrial fuel. World J Microbiol Biotechnol 2013; 30:19-31. [PMID: 23824663 DOI: 10.1007/s11274-013-1415-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 06/23/2013] [Indexed: 11/28/2022]
Abstract
L-Proline (pyrrolidine-2-carboxylic acid) is a distinctive metabolite both biochemically and biotechnologically and is currently recognized to have a cardinal role in gene expression and cellular signaling pathways in stress response. Proline-fueled mitochondrial metabolism involves the oxidative conversion of L-Proline to L-Glutamate in two enzymatic steps by means of Put1p and Put2p that help Saccharomyces cerevisiae to respond to changes in the nutritional environment by initiating the breakdown of L-Proline as a source for nitrogen, carbon, and energy. Compartmentalization of L-Proline catabolic pathway implies that extensive L-Proline transport must take place between the cytosol where its biogenesis via Pro1p, Pro2p, Pro3p occurs and mitochondria. L-Proline uptake in S. cerevisiae purified and active mitochondria was investigated by swelling experiments, oxygen uptake and fluorimetric measurement of a membrane potential generation (ΔΨ). Our results strongly suggest that L-Proline uptake occurs via a carried-mediated process as demonstrated by saturation kinetics and experiments with N-ethylmaleimide, a pharmacological compound that is a cysteine-modifying reagent in hydrophobic protein domains and that inhibited mitochondrial transport. Plasticity of S. cerevisiae cell biochemistry according to background fluctuations is an important factor of adaptation to stress. Thus L-Proline → Glutamate route feeds Krebs cycle providing energy and anaplerotic carbon for yeast survival.
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Affiliation(s)
- Maria Luigia Pallotta
- Department of Medicine and Health Sciences, University of Molise, 86100, Campobasso, Italy,
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28
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Phang JM, Liu W, Hancock C. Bridging epigenetics and metabolism: role of non-essential amino acids. Epigenetics 2013; 8:231-6. [PMID: 23422013 PMCID: PMC3669115 DOI: 10.4161/epi.24042] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Recent research suggests that chromatin-modifying enzymes are metabolic sensors regulating gene expression. Epigenetics is linked to metabolomics in response to the cellular microenvironment. Specific metabolites involved in this sensing mechanism include S-adenosylmethionine, acetyl-CoA, alphaketoglutarate and NAD+. Although the core metabolic pathways involving glucose have been emphasized as the source of these metabolites, the reprogramming of pathways involving non-essential amino acids may also play an important role, especially in cancer. Examples include metabolic pathways for glutamine, serine and glycine. The coupling of these pathways to the intermediates affecting epigenetic regulation occurs by “parametabolic” mechanisms. The metabolism of proline may play a special role in this parametabolic linkage between metabolism and epigenetics. Both proline degradation and biosynthesis are robustly affected by oncogenes or suppressor genes, and they can modulate intermediates involved in epigenetic regulation. A number of mechanisms in a variety of animal species have been described by our laboratory and by others. The challenge we now face is to identify the specific chromatin-modifying enzymes involved in coupling of proline metabolism to altered reprogramming of gene expression.
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Affiliation(s)
- James M Phang
- Metabolism and Cancer Susceptibility Section; Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, NIH, Frederick, MD USA.
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29
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Natarajan SK, Zhu W, Liang X, Zhang L, Demers AJ, Zimmerman MC, Simpson MA, Becker DF. Proline dehydrogenase is essential for proline protection against hydrogen peroxide-induced cell death. Free Radic Biol Med 2012; 53:1181-91. [PMID: 22796327 PMCID: PMC3432146 DOI: 10.1016/j.freeradbiomed.2012.07.002] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/22/2012] [Accepted: 07/06/2012] [Indexed: 12/27/2022]
Abstract
Proline metabolism has an underlying role in apoptotic signaling that influences tumorigenesis. Proline is oxidized to glutamate in the mitochondria, with the rate-limiting step catalyzed by proline dehydrogenase (PRODH). PRODH expression is inducible by p53, leading to increased proline oxidation, reactive oxygen species formation, and induction of apoptosis. Paradoxical to its role in apoptosis, proline also protects cells against oxidative stress. Here we explore the mechanism of proline protection against hydrogen peroxide stress in melanoma WM35 cells. Treatment of WM35 cells with proline significantly increased cell viability, diminished oxidative damage of cellular lipids and proteins, and maintained ATP and NADPH levels after exposure to hydrogen peroxide. Inhibition or siRNA-mediated knockdown of PRODH abolished proline protection against oxidative stress, whereas knockdown of Δ(1)-pyrroline-5-carboxylate reductase, a key enzyme in proline biosynthesis, had no impact on proline protection. Potential linkages between proline metabolism and signaling pathways were explored. The combined inhibition of the mammalian target of rapamycin complex 1 (mTORC1) and mTORC2 eliminated proline protection. A significant increase in Akt activation was observed in proline-treated cells after hydrogen peroxide stress along with a corresponding increase in the phosphorylation of the forkhead transcription factor class O3a (FoxO3a). The role of PRODH in proline-mediated protection was validated in the prostate carcinoma cell line PC3. Knockdown of PRODH in PC3 cells attenuated phosphorylated levels of Akt and FoxO3a and decreased cell survival during hydrogen peroxide stress. The results provide evidence that PRODH is essential in proline protection against hydrogen peroxide-mediated cell death and that proline/PRODH helps activate Akt in cancer cells.
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Affiliation(s)
- Sathish Kumar Natarajan
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Weidong Zhu
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Xinwen Liang
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Lu Zhang
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Andrew J. Demers
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Matthew C. Zimmerman
- Department of Cellular and Integrative Physiology and Redox Biology Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Melanie A. Simpson
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Donald F. Becker
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
- Address correspondence to: Donald F. Becker, Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, N258 Beadle Center, Lincoln, NE 68588, Tel. 402-472-9652; Fax. 402-472-7842;
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Phang JM, Liu W, Hancock C, Christian KJ. The proline regulatory axis and cancer. Front Oncol 2012; 2:60. [PMID: 22737668 PMCID: PMC3380417 DOI: 10.3389/fonc.2012.00060] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 05/27/2012] [Indexed: 12/21/2022] Open
Abstract
Studies in metabolism and cancer have characterized changes in core pathways involving glucose and glutamine, emphasizing the provision of substrates for building cell mass. But recent findings suggest that pathways previously considered peripheral may play a critical role providing mechanisms for cell regulation. Several of these mechanisms involve the metabolism of non-essential amino acids, for example, the channeling of glycolytic intermediates into the serine pathway for one-carbon transfers. Historically, we proposed that the proline biosynthetic pathway participated in a metabolic interlock with glucose metabolism. The discovery that proline degradation is activated by p53 directed our attention to the initiation of apoptosis by proline oxidase/dehydrogenase. Now, however, we find that the biosynthetic mechanisms and the metabolic interlock may depend on the pathway from glutamine to proline, and it is markedly activated by the oncogene MYC. These findings add a new dimension to the proline regulatory axis in cancer and present attractive potential targets for cancer treatment.
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Affiliation(s)
- James Ming Phang
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, Frederick National Laboratory for Cancer ResearchFrederick, MD, USA
| | - Wei Liu
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, Frederick National Laboratory for Cancer ResearchFrederick, MD, USA
| | - Chad Hancock
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, Frederick National Laboratory for Cancer ResearchFrederick, MD, USA
| | - Kyle J. Christian
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, Center for Cancer Research, Frederick National Laboratory for Cancer ResearchFrederick, MD, USA
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Expression in Escherichia coli of the catalytic domain of human proline oxidase. Protein Expr Purif 2012; 82:345-51. [PMID: 22333530 DOI: 10.1016/j.pep.2012.01.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 01/25/2012] [Accepted: 01/27/2012] [Indexed: 12/22/2022]
Abstract
The human PRODH gene has been shown to have unique roles in regulating cell survival and apoptotic pathways and it has been related to velocardiofacial syndrome/DiGeorge syndrome and increased susceptibility to schizophrenia. It encodes for the flavoprotein proline oxidase (PO), which catalyzes the conversion of l-proline to Δ(1)-pyrroline-5-carboxylate. Despite the important physiological and medical interest in human PO, up to now only microbial homologues of PO have been expressed as recombinant protein and fully characterized. By using a bioinformatics analysis aimed at identifying the catalytic domain and the regions with a high intrinsic propensity to structural disorder, we designed deletion variants of human PO that were successfully expressed in Escherichia coli as soluble proteins in fairly high amounts (up to 10mg/L of fermentation broth). The His-tagged PO-barrelN protein was isolated as an active (the specific activity is 0.032U/mg protein), dimeric holoenzyme showing the typical spectral properties of FAD-containing flavoprotein oxidases. These results pave the way for elucidating structure-function relationships of this human flavoenzyme and clarifying the effect of the reported polymorphisms associated with disease states.
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32
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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